State Enforcement of School Immunization Requirements and Child Vaccination Rates

• In Event: Health Policy for Children

Abstract

Child vaccination rates in the U.S. are on the decline. In 39 states, the measles vaccination rate for kindergartners has fallen below 95 percent, a commonly cited threshold for herd immunity (Fine et al. 2011). A direct result of falling vaccination rates is that young children today are increasingly vulnerable to infectious disease outbreaks (Omer et al. 2009). Despite the fact that the CDC declared measles eliminated in 2000, notable outbreaks have recently occurred in several states. In 2025, Texas witnessed the first measles death in over a decade.

Several states have responded to declining vaccination rates by passing legislation to repeal non-medical vaccine exemptions for children in school. This project seeks to understand the impact of non-medical exemption repeal on vaccination rates. The staggered adoption of non-medical exemption repeals across four states (California, New York, Maine, and Connecticut) lends itself to a staggered difference-in-differences approach. Using data on vaccination rates from the CDC and state laws from LexisNexis, we find that state repeal of non-medical exemptions raised kindergarten vaccination rates by 2 to 4 percentage points. We observe little substitution toward medical vaccine exemptions in response to repeals. We demonstrate the robustness of our results to different sample definitions, controls, and estimators. Effects are similar before and after the Covid-19 pandemic, which suggests that state exemption policy plays a critical role in keeping vaccination rates high. In the face of rising vaccine hesitancy, all four states that repealed exemptions were above the threshold for herd immunity in 2023.

While state restrictions on vaccine exemptions can compel families to vaccinate their children, state enforcement may be necessary to ensure compliance. We use the example of the California Department of Education, which began conducting immunization audits in 2021. The goal of the audits was to ensure that unvaccinated students were excluded from school attendance calculations, which can affect school funding. Audits were targeted to schools with greater than 10 percent vaccine non-compliance among kindergarten students. We explore the effects of auditing using the 10 percent threshold in a regression discontinuity (RD) design. We find no evidence of improved vaccine compliance in future years for schools at the audit threshold. We conclude that state enforcement of immunization and attendance rules, while important for proper allocation of state funding, does not raise itself raise vaccination rates.

Our work provides timely evidence on the role of state exemption policy for increasing vaccination rates in the face of rising vaccine hesitancy. It remains an open question how families respond to changing state education and health policy, which will be explored in future work.

Authors

• Samantha Gold, Cornell University
  Presenting Author

• Anthony Bald, California State University, Fullerton
  Non-Presenting Co-Author